The invention relates to a building foundation and floor assembly, and method of installation thereof, in particular for use in residential house construction.
Foundations for houses are usually constructed using temporary concrete forms installed on load bearing earth and extending around a perimeter of the building. Flowable foundation material, such as concrete, is poured into spaces between the forms and allowed to harden, after which the temporary forms are manually removed.
This method of foundation construction incurs many problems, particularly relating to the uneven ground conditions which require considerable preparation by on-side labour. Height and location of the forms must be controlled accurately, both with respect to horizontal and vertical locations. When constructing in inclement weather conditions, such as heavy rain, snow or freezing conditions, difficulties of achieving dimensional accuracy are compounded. Furthermore, when the foundations have been poured, much of the temporary form work cannot be reused, resulting in wastage of forming material.
In some circumstances, in particular with relatively high form work, hydraulic pressure of a column of poured concrete can cause lower portions of the forms to shift upwardly, called "form uplift". This can cause severe problems.
When a prior art foundation has hardened, the wooden structure of the building is secured to an upper surface of the concrete. Typically, this upper surface is relatively rough, and is not completely level, and thus when horizontal wooden strips, called plates, are mounted on the upper surface, they are supported in an uneven manner, and subjected to twisting and bending. The plates are usually secured to the concrete by vertical threaded rods or sheet metal strips set in the concrete before the concrete is cured. The plates are secured to the rods by drilling holes in the plates to accept the rods, and securing the plates to the rods with nuts. Alternatively, the plates can be connected to the sheet metal strips by bending the strips to embrace the plates. Either method of securing the plates to the concrete is relatively inaccurate and subject to error, which has to be corrected at some other stage in construction.
Furthermore, when the floor joists and sub-floor have been installed a master carpenter is required to layout on the sub-floor the positions of interior and exterior walls, doors, windows etc. This is time consuming, and, even when care is taken, is subject to error which results in time consuming corrections later on in the building process.
Many inventions have been developed in attempts to reduce some of the above problems. For example, U.S. Pat. No. 4,711,058 (Patton) discloses a permanent concrete form comprising a metallic sheet permanently connected to an insulated barrier. While this reduces form work wastage, excessive on-site labour and problems of achieving dimensional accuracy remain. U.S. Pat. Nos. 3,673,750 (Bokvist el al) and 3,956,859 (Eingestrom) discloses heat and moisture insulating blocks placed around the perimeter of a foundation prior to pouring concrete. Excessive on-site labour, high foundation material costs and difficulty in maintaining accuracy still remain. U.S. Pat. No. 4,799,348 (Brami et al) discloses insulating a rigid slab for carrying a building but this also requires excessive on-site labour for site preparation, installation of recoverable forms and the need for accurate location of same. U.S. Pat. No. 4,689,926 (MacDonald) discloses a method of providing an insulating structure beneath a building or platform, as opposed to a true foundation. In this method the building is initially supported above a shell of resilient plastic material to define a space between the building and the shell, which space is substantially entirely filled with insulating foam. This is costly and would appear to be appropriate only for small buildings, such as mobile homes.
In the inventor's opinion, many of the inventions relating to building foundations disclosed in the patents above do not provide large reductions in on-site labour, nor reduce the necessity for accurate location of forms or placement of foundation material. Furthermore, none of the patents above disclose a means for eliminating the costly and time consuming layout necessary to mark a sub-floor with locations of exterior and interior walls as previously described.